Optical encoders are well known and employed for a variety of applications. For example, a high-resolution optical encoder may be utilized to measure a relative position of an object by providing a count signal and a direction signal in response to position movements of the object. To determine an absolute position of the object, the object is typically moved to a known, repeatable position referred to as the “home” position. Additional sensors and/or fixtures (e.g., hard stops or limit switches) are generally required for determining the home position.
An electronic counter of the optical encoder is typically reset to zero at the home position. The count and direction signals generated due to differential movement from this absolute home position are utilized to update the electronic counter. Consequently, by knowing the amount of movement required to generate a count signal and the count associated with the home position (e.g., a count of zero), the absolute position of the object can be determined from the present count.
One drawback of this type of optical encoder is that after the home position is determined, the integrity of the count and direction signals must be maintained. For example, a momentary power loss or signal interruption (e.g., a signal glitch) will result in invalid position information. Additionally, the object's motion (e.g., velocity) must be limited so that the rate at which the count signals are generated does not exceed the counter's capabilities. As a result, there is a need for providing improved position measurement techniques.